He needs his lux meter reading taken at the same distance.
1 microwatt per square cm = 10000 microwatts per square meter
1 lux =1 lumen per square meter
So multiply microwatts per square cm by 10 000 to microwatts per square meter and divide it by the lux reading taken at the same distance and that’ll give him UV as microwatts per lumen.
-Doug
Douglas Nishimura
Image Permanence Institute
Rochester Institute of Technology
From: Museum discussion list [mailto:[log in to unmask]]
On Behalf Of Marc A Williams
Sent: Wednesday, February 01, 2017 6:12 PM
To: [log in to unmask]
Subject: Re: [MUSEUM-L] measuring UV levels
Emanuele,
One explanation is that the bulbs already have some sort of UV filtration, so the filters are starting with this already reduced level. Do you recall the conversion from microwatts
per centimeter to microwatts per lumen? The museum/conservation world runs on the latter, so knowing what that figure is may be illuminating. The other possibility is that the film does not meet specs. Try putting the film over a window pane and measuring
the same exact spot with and without the film (make sure a cloud does not come over the sun) and see what the difference is. If the UV only drops 25% or 50% or even 75%, the film is junk. It should reduce UV something like 99%. Good luck.
Marc
American Conservation Consortium, Ltd.
4 Rockville Road
Broad Brook, CT 06016
www.conservator.com
860-386-6058
Marc A. Williams, President
MS in Art Conservation, Winterthur Museum Program
Former Chief Wooden Objects Conservator, Smithsonian Institution
Fellow, American Institute for Conservation (AIC)
From:
Marconi, Emanuele
Sent: Wednesday, February 01, 2017 4:31 PM
Subject: [MUSEUM-L] measuring UV levels
I recently bought UV filtering films from a supplier for the fluorescent lamps I have in the lab.
I did a test measuring the UV levels without the film and it was around 45 microwatts per square centimeter (50 cm of distance from the light). With the film, the level is 30 microwatts per square centimeter.
I am pretty surprised. I would expect a very different reading as the film is supposed to cut the 97% of the emission. I use an UVA/B meter form Sper Scientific (mod. 850009). I can’t check the calibration,
but I used it last time a few months ago and the readings were in line with the ones of a much more expensive museum UV reader.
Thanks,
Emanuele
EMANUELE MARCONI
Conservator
National Music Museum
University of South Dakota
414 E. Clark St., Vermillion SD 57069
www.nmmusd.org
+1 (605) 677-5093
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